Performance enhancement of PEM electrolyzers through iridium-coated titanium porous transport layers

Published on December 1st, 2018. Titanium-based porous transport layers (PTL) used in polymer electrolyte membrane (PEM) water electrolyzers suffer from surface passivation (titanium oxidation), which increases the interface resistance between the PTL and electrode. For long-term operation, PTLs are typically coated with considerable amounts of platinum or gold to ensure reasonable performance profiles over time. Moreover, it is well known that the oxide forms of platinum and gold are not stable under electrolysis conditions. In this study, an easy and scalable method is introduced to protect the titanium PTL from passivation by sputtering very thin layers of iridium onto commercially-available titanium PTLs. The iridium layer reduces the overall ohmic resistance of the PTL/catalyst layer interface and improves the cell's performance to that achieved with carbon-based PTLs. The coating process homogeneously deposited iridium throughout the inner structure of the PTL. The findings of this study may lead to the use of iridium as a protective layer for titanium PTLs, potentially enable operation at increased cell voltages and lead to increased electrolyzer durability.